Silicone sealants are important products for structural glazing and weather sealing applications for the construction industry. The durability of silicone sealants is due in part to their elastomeric character that allows for warranty coverage of 20 years or more. However, the durable sealant matrix must also maintain adhesion to the various building materials that are used in constructing buildings. In some cases there is a need to prepare or treat the surface with a priming agent in order to provide a reactive surface to which the adhesion promoting components of the sealant can react. Functionalized silanes, organosilicon resins and titanates are commonly employed as priming agents for enhancing adhesion of silicone sealants.
Metal substrates are commonly used in construction, and they are often painted in order to prevent oxidation and to achieve an aesthetically pleasing appearance. Some paints are specifically formulated with fluorinated polymers to provide an inert surface that does not fade in color or attract dirt when used in outside applications, where exposure to UV and particulate can otherwise negatively impact the appearance. These inert surfaces that reduce dirt pick up and oxidation can also make sealant adhesion challenging. Thus, these inert surfaces often require a priming step to enable the durability warranty. Duranar® and Duracron® (both available from PPG Industries, Inc., Cleveland, Ohio) are common brands of paints used on metal substrates for construction.
There are numerous primers that are available for use in construction applications. Typically, these primers consist of reactive silanes, resins and/or other adhesion promoting molecules that are dissolved in solvents to improve the uniform coating of the surface to maximize adhesion development. These solvents release volatile organic compounds (VOCs) into the atmosphere. Because many commonly used solvents are known to contribute to lowering air quality, there are regulatory pressures to reduce their use in almost every country throughout the world. Government Agencies like the United States Environmental Protection Agency (EPA) and states like California have placed limits on the VOC content of primers used in their jurisdictions. Various other government agencies and states have placed similar restrictions on the use of VOCs.
Therefore, there is currently a need for a more ecologically friendly primer to reduce air pollution and meet the VOC restrictions set by government agencies. Additional requirements for robust, durable adhesion to facilitate offering the desired warranty for building owners also need to be addressed. The embodiments disclosed herein address that need.
The present disclosure allows for use of solvents that are considered VOC exempt per certain government agencies, including the United States EPA and the state of California, while also improving adhesion durability.